<!DOCTYPE html><html><head><meta http-equiv="Content-Type" content="text/html; charset=utf-8" /></head><body>Dear Andrea,<div><br></div><div>Thanks alot for your great explanation.</div><div><br></div><div>With my best wishes,</div><div><br></div><div> Mutlu.</div><div><br><br><div><div class="crea-font-wrapper" style="font-family: Tahoma; font-size: 16px;">------------------------------------------</div><div class="crea-font-wrapper" style="font-family: Tahoma; font-size: 16px;">Dr. Mutlu ÇOLAKOĞULLARI</div><div class="crea-font-wrapper" style="font-family: Tahoma; font-size: 16px;">Trakya Universitesi </div><div class="crea-font-wrapper" style="font-family: Tahoma; font-size: 16px;">Fen Fakultesi</div><div class="crea-font-wrapper" style="font-family: Tahoma; font-size: 16px;">Fizik Bolumu</div><div class="crea-font-wrapper" style="font-family: Tahoma; font-size: 16px;">22030 Merkez-EDİRNE</div><div class="crea-font-wrapper" style="font-family: Tahoma; font-size: 16px;"><br></div><div class="crea-font-wrapper" style="font-family: Tahoma; font-size: 16px;"><span style="font-family: 'times new roman', 'new york', times, serif; font-size: 16.3636360168457px;">> Dear Carlo, Andrea and Paolo;</span><br style="font-family: 'times new roman', 'new york', times, serif; font-size: 16.3636360168457px;"><span style="font-family: 'times new roman', 'new york', times, serif; font-size: 16.3636360168457px;">> The taking responds and advices from people who has experienced makes me happy.</span><br style="font-family: 'times new roman', 'new york', times, serif; font-size: 16.3636360168457px;"><span style="font-family: 'times new roman', 'new york', times, serif; font-size: 16.3636360168457px;">> As Paolo and Carlo also said, cif2qe.sh is not working properly, (at least for this case). Therefore, I used the other codes for double cross check: pymatgen and cif2cell. The conventional cell has 64 atoms whereas its primitive has 32 atoms. </span><br style="font-family: 'times new roman', 'new york', times, serif; font-size: 16.3636360168457px;"><span style="font-family: 'times new roman', 'new york', times, serif; font-size: 16.3636360168457px;">> Pymatgen is very proper for POSCAR output because it takes symmetry analysis depend on Curtarolo-Setyawan's paper [</span><a href="http://arxiv.org/abs/1004.2974v1" target="_blank" style="margin: 0px; padding: 0px; text-decoration: underline; color: rgb(25, 106, 212); outline: none; font-family: 'times new roman', 'new york', times, serif; font-size: 16.3636360168457px; background-image: initial; background-attachment: initial; background-size: initial; background-origin: initial; background-clip: initial; background-position: initial; background-repeat: initial;">http://arxiv.org/abs/1004.2974v1</a><span style="font-family: 'times new roman', 'new york', times, serif; font-size: 16.3636360168457px;">] (MCLC5 - it gives also gamma angle, for this case)...so, it is not matching with QE's ibrav settings depend on cell vectors. Cif2Cell code gives the exactly same CELL_PARAMETERS card with Quantum-ESPRESSO's ibrav=-13...that is the reason why I chose Cif2Cell code.</span><br style="font-family: 'times new roman', 'new york', times, serif; font-size: 16.3636360168457px;"><span style="font-family: 'times new roman', 'new york', times, serif; font-size: 16.3636360168457px;">> Andrea, it was my fault. I had been complicated among space groups(2/m for sg:12 and 2/C for sg:15) and Herman-Mauguin notations(2/m for space groups 12-15). You said that ?Using ibrav=-13 it is not necessary to add these atoms in the list of atoms inside the unit cell." Andrea, you mean that could I decrease the number of atoms in primitive cell if they have symmetrized by last 4 symmetry operations in this case? By this way, the cell lost half of atoms inside which is good news for computational resources. </span><br style="font-family: 'times new roman', 'new york', times, serif; font-size: 16.3636360168457px;"><span style="font-family: 'times new roman', 'new york', times, serif; font-size: 16.3636360168457px;">> </span><br style="font-family: 'times new roman', 'new york', times, serif; font-size: 16.3636360168457px;"><span style="font-family: 'times new roman', 'new york', times, serif; font-size: 16.3636360168457px;">I think so. As far as I understand there are two possibilities:</span><br style="font-family: 'times new roman', 'new york', times, serif; font-size: 16.3636360168457px;"><span style="font-family: 'times new roman', 'new york', times, serif; font-size: 16.3636360168457px;">1) You apply all the 8 symmetry operations and use ibrav=-12 (simple</span><br style="font-family: 'times new roman', 'new york', times, serif; font-size: 16.3636360168457px;"><span style="font-family: 'times new roman', 'new york', times, serif; font-size: 16.3636360168457px;">monoclinic) obtaining 64 atoms.</span><br style="font-family: 'times new roman', 'new york', times, serif; font-size: 16.3636360168457px;"><span style="font-family: 'times new roman', 'new york', times, serif; font-size: 16.3636360168457px;">2) You apply only the first four symmetry operations and use ibrav=-13</span><br style="font-family: 'times new roman', 'new york', times, serif; font-size: 16.3636360168457px;"><span style="font-family: 'times new roman', 'new york', times, serif; font-size: 16.3636360168457px;">(one base centered monoclinic). Note however that in this case you have</span><br style="font-family: 'times new roman', 'new york', times, serif; font-size: 16.3636360168457px;"><span style="font-family: 'times new roman', 'new york', times, serif; font-size: 16.3636360168457px;">to refer the positions to the base centered monoclinic axes, while the</span><br style="font-family: 'times new roman', 'new york', times, serif; font-size: 16.3636360168457px;"><span style="font-family: 'times new roman', 'new york', times, serif; font-size: 16.3636360168457px;">positions that you obtain applying the symmetry are still referred to</span><br style="font-family: 'times new roman', 'new york', times, serif; font-size: 16.3636360168457px;"><span style="font-family: 'times new roman', 'new york', times, serif; font-size: 16.3636360168457px;">the simple monoclinic cell. The base centered monoclinic cell has one</span><br style="font-family: 'times new roman', 'new york', times, serif; font-size: 16.3636360168457px;"><span style="font-family: 'times new roman', 'new york', times, serif; font-size: 16.3636360168457px;">half the number of atoms of the simple monoclinic cell.</span><br style="font-family: 'times new roman', 'new york', times, serif; font-size: 16.3636360168457px;"><br style="font-family: 'times new roman', 'new york', times, serif; font-size: 16.3636360168457px;"><span style="font-family: 'times new roman', 'new york', times, serif; font-size: 16.3636360168457px;">In no cases however QE will find 8 symmetry operations. In the first</span><br style="font-family: 'times new roman', 'new york', times, serif; font-size: 16.3636360168457px;"><span style="font-family: 'times new roman', 'new york', times, serif; font-size: 16.3636360168457px;">case because fractional translations will be disabled (the cell is</span><br style="font-family: 'times new roman', 'new york', times, serif; font-size: 16.3636360168457px;"><span style="font-family: 'times new roman', 'new york', times, serif; font-size: 16.3636360168457px;">actually a supercell). In the second case because there are only 4.</span><br style="font-family: 'times new roman', 'new york', times, serif; font-size: 16.3636360168457px;"><span style="font-family: 'times new roman', 'new york', times, serif; font-size: 16.3636360168457px;">It is not a question of notations, the point group for the space group</span><br style="font-family: 'times new roman', 'new york', times, serif; font-size: 16.3636360168457px;"><span style="font-family: 'times new roman', 'new york', times, serif; font-size: 16.3636360168457px;">C2/c is C_2h (that has 4 operations), there is no way to obtain a larger</span><br style="font-family: 'times new roman', 'new york', times, serif; font-size: 16.3636360168457px;"><span style="font-family: 'times new roman', 'new york', times, serif; font-size: 16.3636360168457px;">point group.</span><br style="font-family: 'times new roman', 'new york', times, serif; font-size: 16.3636360168457px;"><br style="font-family: 'times new roman', 'new york', times, serif; font-size: 16.3636360168457px;"><span style="font-family: 'times new roman', 'new york', times, serif; font-size: 16.3636360168457px;">HTH,</span><br style="font-family: 'times new roman', 'new york', times, serif; font-size: 16.3636360168457px;"><br style="font-family: 'times new roman', 'new york', times, serif; font-size: 16.3636360168457px;"><span style="font-family: 'times new roman', 'new york', times, serif; font-size: 16.3636360168457px;">Andrea</span><br></div></div></div></body></html>